Refrigerated containers, as containers for meeting requirements in heat-insulating, refrigerating and freezing of goods, can attain an objective of delaying spoilage of goods contained therein by controlling atmosphere, temperature, and humidity inside the containers by means of, for example, preservation measures and air-conditioning measures. For many years, to ensure a safe transportation, the refrigerated containers always, like those general containers, use a mechanical closure with a globally unique identification code to lock a locking handle of the container door panels. Thus, it could be easily determined whether the container has been tampered during transport. However, the mechanical closure has a drawback of being susceptible to destruction and camouflage, thus resulting in a poor level of security.
To achieve real-time monitoring of the container during its transportation, an electric closure has emerged in place of the mechanical closure. Once the electric closure is unauthorizedly opened, a monitoring module of the electric closure will emit alarming signals via an antenna. However, since the electric closure works by locking a locking handle into a corresponding handle seat, and rivets for mounting the handle seat on the door panel is susceptible to destruction and camouflage, a security level of the electric closure is greatly impaired.
To better monitor unauthorized opening of the container door, a technical solution about a safety container is disclosed in a Chinese patent application No. 200410056197.7 filed on Aug. 18, 2004. In this technical solution, a detection plate is arranged on an inner side of one of the two door panels of the container. A monitoring module, a displacement sensor and an antenna which are integrally formed are correspondingly arranged on the other one of the door panels. The displacement sensor and the antenna are arranged to protrude from two opposite side surfaces of the monitoring module around one end portion thereof. Further, the displacement sensor protrudes towards an interior of the container and cooperates with the detection plate, and the antenna protrudes out of the container via a hole formed in the container door panels. Once the door is unauthorizedly opened, a relative displacement will occur between the two door panels, and thus the displacement sensor detects such a displacement and sends a signal indicating that the door is unauthorizedly opened to the monitoring module, and then the monitoring module emits alarming signals via the antenna.
To some extent, the technical solution described above may solve the problem of determining whether the general container door is unauthorizedly opened. However, certain disadvantages will be caused when the above-mentioned technical solution is applied in a refrigerated container provided with a foamed heat insulating layer which serves to prevent a heat exchange between inside and outside of the container. On the one hand, integrally formed displacement sensor, antenna and monitoring module are not easily mounted in the door. On the other hand, the displacement sensor and the antenna respectively protruding towards the interior and exterior of the container at the end portion of the monitoring module will damage initial structures of the heat insulating layer of the container door so as to cause a heat exchange between inside and outside of the container and thus deteriorate a heat-insulating performance of the refrigerated container door panels.